Modern industrial manufacturing processes often involve the utilization of emulsifiable oil or non-petroleum water-soluble formulations in cutting and grinding operations. The emulsifiable oil and non-petroleum water-soluble formulations include lubricants and cutting fluids and are used, for example, in the grinding and smoothing of edges of manufactured glass products and in the machining of cast iron objects. The emulsifiable oil formulations are commonly referred to as "water-soluble oils" in the parlance of the industry. Due to their similarity of function, we will refer to the lubricants and the cutting fluids collectively by the term "water-soluble lubricants."
Water-soluble lubricants commonly contain a number of components which help reduce heat generation thereby extending tool life and improving surface finish. These lubricants also tend to lubricate and reduce or prevent corrosion in moving parts located near to the cutting or grinding tool. A typical water-soluble lubricant used in glass grinding operations might contain: (a) triethanolamine salt of an acid phosphate ester to reduce heat caused by extreme pressure at the cutting surfaces, and to reduce corrosion; and (b) water to cool the cutting surfaces. A typical water-soluble lubricant used in the machining of cast iron might contain: (a) triethanolamine caprylate to reduce corrosion and enhance lubricity; (b) sodium nitrite to prevent corrosion; (c) polyalkylene glycol as a lubricating and anti-wear agent; and (d) water to cool the cutting surfaces.
Due to economic and other considerations, it is desirable to reuse water-soluble lubricants. Each time the lubricants are used, particles of the material being ground or cut become suspended in the lubricant and impair its further usefulness. In glass grinding operations, silica particles and metallic oxides become suspended in the water-soluble lubricant; in cast iron machining processes, iron and graphitic particles become suspended in the water-soluble lubricant. The suspended particles tend to clog grinding wheels and to cause dulling of cutters, requiring premature tool replacement and impairing the quality of the surface finishes. Also, the suspended particles may interfere with the operation of pumping and circulating apparatus.